1. Field of the Invention
This invention relates to an ink jet recovery device from recovering from unsatisfactory discharge including the ink non-discharge of an ink jet recording head, and an ink jet recording apparatus having such ink jet recovery device.
2. Related Background Art
In ink jet recording apparatuses, to prevent the clogging of ink discharge ports provided in the recording head or the mixing of air from the ink discharge ports from causing unsatisfactory discharge of ink, there is in some cases provided an ink recovery device for sucking ink from the ink discharge ports and thereby normalizing the ink discharge state.
The conventional ink recovery device of this type, however, has suffered from a problem that for the unsatisfactory discharge caused by the mixing of air in the recording head, only the ink is sucked and the air particularly at the corner or the stepped portion in the recording head is not sucked and discharged and the discharge state remains unstable.
In FIG. 1 of the accompanying drawings, there is shown the construction of the conventional ink recovery device. A plurality of discharge ports 1E in a recording head 1 are hermetically sealed by a cap 3 to which are connected a suction tube 4 and an atmosphere-open tube 5. The other end of the suction tube 4 is connected to a suction pump 6 which is a negative pressure generating source. The atmosphere-open tube 5 is provided with a vent valve 7 and an electromagnetic valve 8, the opening and closing of which is controlled by an electromagnetic valve opening-closing control timer 9. An ink absorbing member 2 capable of absorbing and retaining ink is provided in the cap 3. The vent valve 7 is operatively associated with the operating lever of the suction pump 6, and is adapted to be closed during ink suction and to be opened during the capping for preventing the evaporation of ink in the ink discharge ports and the adherence of dust to the ink discharge ports. The electromagnetic valve 8 is normally closed, but may be opened by the electromagnetic valve opening-closing control timer 9 at a timing which will be described later to thereby communicate the atmosphere-open tube 5 with the atomsphere.
The operation of the above-described ink recovery device will hereinafter be described with reference to the timing chart of FIG. 2 of the accompanying drawings.
When the suction pump 6 is turned ON (operative state) at a point of time t0 in FIG. 2 with the discharge ports 1E hermetically sealed by the cap 3 and with the vent valve 7 and the electromagnetic valve 8 closed, air is sucked in through the suction tube 4 and negative pressure (for sucking the ink) is produced in the cap 3 and in the atmosphere-open tube 5 and thus, the ink is sucked in from the discharge ports 1E. The ink thus sucked in fills the cap 3 and overflows from the ink absorbing member 2. In some cases, the atmosphere-open tube 5 is also filled with the ink. However, this state, if continued, will adversely affect the ink discharge thereafter. So, at a point of time t1 in a predetermined time after the point of time t0, the electromagnetic valve 8 is turned ON (opened state) to thereby communicate the atmosphere-open tube 5 with the atmosphere. Thereupon, the ink overflowing from the ink absorbing member 2 and the ink in the atmosphere-open tube 5 are sent to the suction pump 6 through the suction tube 4.
As shown in FIG. 2, the pressure in the cap 3 (the suction pressure waveform) becomes negative pressure with some rising angle at the point of time t0 whereat the suction pump 6 has been turned ON, and abruptly restores the atmospheric pressure at the point of time t1 whereat the electromagnetic valve 8 has been turned ON (opened). Accordingly, after the point of time t1, ink suction does not take place. The time t1-t0 from the point of time t0 at which the suction pump 6 is turned ON till the point of time t1 at which the electromagnetic valve 8 is turned ON is controlled by the electromagnetic valve opening-closing control timer 9. Also, this time t1-t0, i.e., the ink suction time, can be varied by adjusting the electromagnetic valve opening-closing control timer 9.
Heretofore, unsatisfactory discharge has been eliminated by the negative pressure suction sequence of FIG. 2. However, particularly when bubbles 1C are present in the common ink chamber 1B rearward of the liquid path 1A of the recording head 1 as shown in FIG. 1, unsatisfactory discharge has been liable to occur and recovery has been difficult. Also, when bubbles are present in the corner and stepped portion in the common ink chamber 1B, even if the ink is sucked by the negative pressure of the suction pump 6, the ink has flowed toward the discharge ports 1E only in the portion of the interior of the common ink chamber 1B through which the ink is ready to flow and the bubbles 1C have remained stagnant and as a result, unsatisfactory discharge has been difficult to eliminate.